1. Field of the Invention
The present invention relates to a method of inhibiting spermatogenesis by injecting a chemical sterilant in a manner that promotes its effectiveness so that a lower dose is required for sterilization of an animal.
2. Brief Description of the Prior Art
Sterilization of male animals to limit reproduction in pets and livestock is usually effected by surgical castration. Surgery requires skilled personnel, a surgical suite with associated equipment and there are risks (e.g., anesthesia, infection and hemorrhage). A more humane and less costly method has been sought.
Many compounds have been explored for the purpose of arresting spermatogenesis chemically. Hormonal methods have been proposed but a method wherein the sterilant is injected into the testes is preferred because it exposes only the sperm producing tissue to the compound, thus avoiding direct distribution of foreign chemicals to non-reproductive tissues in the body. An injection into the testis also requires less skill than surgery to perform, opening the possibility that the procedure can also be practiced in developing and third world nations.
Various chemical agents have been injected into the testis for the purpose of interfering with the production of sperm in the seminiferous tubules. Many effective chemicals have been found too harsh to be used practically. An effective and biologically acceptable chemical sterilant was described in U.S. Pat. Nos. 4,937,234 and 5,070,080 to Fahim. In the '080 patent, the chemical sterilant was injected into the midline of the testis along the side or at the bottom of the testis. Depending upon the dose administered, spermatogenesis in the seminiferous tubules was completely stopped, effecting sterilization of the animal. It is preferred to administer the lowest possible effective amount but this gives rise to a chance that some portion of the testis will be left intact. If this occurs there is a possibility that a few sperm may reach the head of the epididymis. In view of the above, there is a need for a method of injecting the chemical sterilant described in U.S. Pat. Nos. 4,937,234 and 5,070,080 into a testis in a manner that the transport of any sperm is thwarted.